The present invention relates to an improved method for producing a diaphragm for acoustic appliances, and more particularly relates to an improvement in production of a diaphragm used for acoustic appliances such as speakers and microphones.
Method for producing such a diaphragm are proposed, for example, in Japanese Patent Opening No. Sho. 49-129640 and Japanese Patent Publication No. Sho. 53-4421.
The process proposed in JPO. No. Sho. 49-129640 is directed to production of a beryllium thin plate. The process includes the step of developing a thin beryllium layer of a prescribed thickness on a substrate by means of vacuum evaporation and the step of removing the substrate via dissolution. In the case of this conventional process, the diaphragm obtained is low in density due to the inherent fragility of beryllium and, in particular, evolvement of fine voids. As a consequence, the diaphragm is unable to generate sufficient sound pressure in the high frequency range when used for speakers.
In the process of JPP. No. Sho. 53-4421, a thin beryllium alloy layer containing 0.1 to 15% of aluminum is developed on a substrate and, after heat treatment, the alloy thin layer is separated from the substrate. The heat treatment is carried out, for example, in an argon gas environment at 600.degree. C. to 650.degree. C. for about one hour. In this case, increase in density of the product via the heat treatment has a limit and the resultant density of the product is still insufficient for use as a diaphragm for acoustic appliances. Like the first example, the diaphragm is again unable to generate sufficient sound pressure in the high frequency range.